1. Field of the Invention
The present invention relates to an additive for resist which can suppress leaching caused by water at the time of an immersion lithographic process by increasing the hydrophobicity of the surface of a resist film, and can form a fine resist pattern having excellent sensitivity and resolution, and to a resist composition containing the additive for resist.
2. Description of the Related Art
Along with the recent trend of high integration of large scale integrated circuits (LSI) and an increase in the processing speed, there is a demand for fine fabrication of photoresist patterns. As the exposure light to be used at the time of forming a resist pattern, g-line (436 nm), line (365 nm), or the like of a mercury lamp has been mainly used.
However, as the increase in the resolution that stems from the exposure wavelength approaches a substantial limit, a method of making the exposure wavelength shorter has been suggested as a means for forming a finer photoresist pattern. For example, in particular, a KrF excimer laser (248 nm), an ArF excimer laser, and the like of shorter wavelengths are used instead of the i-line (365 nm).
An ArF immersion lithographic method of using an ArF excimer laser as a light source is characterized by being carried out by enclosing water between a projection lens and a wafer substrate. This method utilizes the refractive index of water at 193 nm, so that even if a lens having a numerical aperture of 1.0 or greater is used, pattern formation is possible, and this method is usually referred to as an immersion exposure method. However, there is a problem that since a resist film is brought into direct contact with pure water, the acid generated by a photoacid generator, or the amine compound that is included in the resist film as a quencher is easily dissolved in water, and thereby, a change in the shape of the resist pattern, pattern destruction caused by swelling, and various defects such as bubble defects and watermark defects occur.
Accordingly, for the purpose of blocking a resist film from a medium such as water, there has been suggested a method of forming a protective film or an upper layer film between the resist film and water. Such a resist protective film is required to have characteristics that the protective film has a sufficient light transmittance at the relevant wavelength so as not to interrupt exposure, can be formed on a resist film without causing intermixing with the resist film, can form and maintain a stable film without being dissolved out in a medium such as water at the time of immersion exposure, and can be easily dissolved in an alkali liquid or the like, which serves as a developing liquid at the time of development.
Patent Document 1: Korean Patent Application Laid-Open No. 2011-0084848 (published on Jul. 27, 2011)
Patent Document 2: Koran Patent Application Laid-Open No. 2008-0000522 (published on Jan. 2, 2008)
Patent Document 3: Korean Patent Application Laid-Open No. 2011-0079649 (published on Jul. 7, 2011)